As a junior, I knew about the switching sides rule, but not the service order. We didn't have the internet back in those days, and I was never given a rule book to read: all knowledge came from those teaching us the game. I don't know if they just omitted telling us, or didn't know themselves! The switching sides rule came up quite regularly as there was always at least one kid who inadvertently ended up on the wrong side mid-set.

Nowadays, I use it mainly to ensure we remain serving from the same end that we did in the first set. I've found that keeping that consistent often leads to better results, unless one partner has a far stronger serve. I can't remember ever having switched sides mid-way through a match.